Interest in reducing the emission of undesirable particulates from sputter targets has increased over the last few years. For example, one study.sup.1 of the subject deals with the effect of target impurity composition and density on the film resistivity, C-V shift and leakage performance. Particle emission effects were not directly measured in this work. FNT .sup.1 T. Brat, D. Pramanik, J. E. Poole and C. E. Wickersham, Jr., Proceedings 2nd ASM International Electronic Materials and Processing Congress, Philadelphia, Pa., April 1989, pp. 241-248.
Waterman et al.sup.2 were first to link target manufacturing processes to particle emission and defect densities on sputter coated wafers. They found that the target manufacturing method had a strong influence on the particle density and the device yield. Their explanation for the result was that oxygen content and "void pressure" in the different targets was partly responsible for the observed results. All targets used in the paper by Waterman et al.sup.2 had a microstructure of some combination of .beta.(Ti,W), a Ti rich phase and a W rich phase. They failed to link directly the particulate emission performance of the targets with the target microstructure. Furthermore, their theory suggests that lowering the processing pressure will result in a lower "void pressure" and thus a lower level of particulate emission. FNT .sup.2 E. Waterman, J. Dunlop, and T. Brat, Proceedings of the 7th IEEE VLSI Multilevel Interconnection Conference, Santa Clara, Calif., June 1990, pp. 329-331.
U.S. Pat. No. 4,838,935 (Dunlop et al) teaches that "voids" in tungsten-titanium targets result in increased "particulates" during sputter coating. Improved targets are purportedly prepared by powder metallurgical techniques using titanium hydride powder or mixtures of titanium power and titanium hydride along with the tungsten powder. Compaction of the powders is effected at a temperature of at least 1350.degree. C. with an optimum temperature range given as 1375.degree.-1450.degree. C. Below this critical temperature range, the patent indicates that the resulting target will not possess the requisite density. Pressure in the range of about 2,000 to 5,000 psi (14 MPa to 34 MPa) is applied to the die.
U.S. Pat. Nos. 4,931,253 (Eylon et al) and 4,714,587 (Eylon et al) teach HIPing (hot isostatic pressing) of titanium alloys at temperatures close to the .alpha.Ti-.beta.Ti phase transformation temperature so that the .alpha.Ti-phase is retained in the finished part. The process reputedly results in fine grain structure and improved mechanical properties. No mention is made of sputter target formation or sputtering in general.